Process of clarifying aqueous suint bath containing grease and scouring raw wool with the purified bath



PROCESS OF CLARIFYING AQUEOUS SUINT BATH CONTAINING GREASE AND SCOURING RAW WOOL WITH THE PURIFIED BATH Filed NOV. 10. 1955 COLLOIDAL BENTONITE RAW 4 WOOL WATER IVHXER SETTLER H WASHING BOWI. WASTE k WASH LIQUOR 'CLARIFIED WASH LIQUOR SLUDGE WASHED w0o| COLLOIDAL BENTONITE R MIXER 2 SGOURING SETTLER BOWL WASTE SCOURING LIQUOR A CLARIFIED 9 SCOURED SCOURING 9 woo| LIQUOR s| uoe Willie Fong IN V ENTOR.

United States Patent PROCESS OF CLARIFYING AQUEOUS SUINT BATH CONTAINING GREASE AND SCOU-R- ING RAW WOOL WITH THE PURIFIED BATH Willie Fong, Richmond, Calif., assignor to the United States of America as represented by the Secretary of Agriculture Application November 10, 1955, Serial No. 546,293

2 Claims. (Cl. 8-139) (Granted under Title 35, U.S. Code (1952), sec. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, for all governmental purposes throughout the World, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the processing of wool and has as its prime object the provision of improved methods for scouring raw wool and clarifying the liquors from such treatment.

Raw wool scouring is the preliminary step in the processing of wool by which the impurities present in the wool are removed by suitable physical or chemical means. The process is of great importance in the success of subsequent operations, such as carding, drawing, spinning, weaving, dyeing, etc.

The nature and the quantity of the impurities in raw wool vary, depending to a certain extent upon the breed of the animal and the geographical, climatic or nutritional conditions under which it is raised. Generally speaking, these impurities may be classified into two broad categories (I) acquired impurities, such as earthy material, vegetable matter, faecal matter, paint, tar, etc., and (2) the natural impurities secreted by the animal.

These natural impurities consist of two major components, wool suint and wool grease. Together these two components are commonly known as wool yolk.

Wool suint is the dried, water-soluble material secreted by the sweat gland of the animal. Chemically, very little is known concerning the exact composition of this substance; however, investigators agree that it consists essentially of the potassium salts of organic acids. Wool suint possesses some detergent power which is utilized in the known aqueous scouring processes as will be explained hereinafter.

The wool grease is a complex water-insoluble mixture secreted by the sebaceous glands of the sheep. This material protects the wool fibers against the elements during its growth. Strictly speaking, the greasy component of Wool is a wax, the ester of a high molecular weight monohydric alcohol and a fatty acid. The component wool wax alcohols consist of three major series: (1) the sterols, principally cholesterol, (2) the tri-terpenelike alcohols, principally lanosterol, and (3) aliphatic alcohols. The component wool wax acids consist of four major series: 1) the normal fatty acids, (2) hydroxy acids, (3) branched chain acids, and (4) iso acids.

Commercially, several different methods are used in wool scouring. One of the widely used processes is the emulsification process in which the major scouring action is performed with a liquor containing soda ash and soap or synthetic detergent. Thus the wool is propelled through an alternating series of bowls and squeeze rolls.

The alkaline liquor containing soda ash and soap or synthetic detergent is introduced into all bowls except the final rinse bowl. In another process, known as the suint on Duhamel process, the wool is first steeped in lukewarm water to dissolve the water-soluble suint salts. This suint solution is then clarified by filtering or centrifuging and returned to the first two bowls in the scouring train as the major scouring agent.

Neither the emulsification nor the suint process are entirely satisfactory for the following reasons. In the case of the emulsification process, the pH of the scouring solution is so high that there is danger of serious damage to the wool fibers. Further, the recovery of the by-products, the suint and the wool grease, from the spent scouring liquor is diflicult. In the suint process the treatment is mild and does not damage the fibers but it does not reduce the grease content of the wool to the low levels required by the industry.

Another disadvantage of the suint process is that the known methods for clarifying the suint solution by the use of filtration or centrifugation have never proved satisfactory in that grease removal is inefiective with the result that the detergent effect of the clarified suint solution is not as high as it might be' were this grease not present. Also such clarification methods require the use of expensive equipment and involve high labor, operating, and maintenance costs so that the process has never been commercially successful.

In recent years another method of wool scouring has received considerable attention from commercial wool processors. In this technique the Wool is scoured with a liquor containing essentially water and a relatively high concentration of a non-ionic detergent. The advantage of such a scouring liquor is that it is efiective at slightly alkaline or even neutral pHs whereby damage to the wool is greatly restricted. The procedure, however, has the disadvantage that the non-ionic detergents are relatively expensive so that the process can only be applied to high grade wools in conjunction with centrifugal grease recovery systems.

It has now been found that wool can be scoured by an elfective and relatively inexpensive method. In essence the process of this invention involves first washing the raw wool with plain water at about room temperature. The washed wool and aqueous liquor are then separated as by wringing or the like. The liquor from this process is largely an aqueous solution of suint extracted from the raw wool together with suspended grease and dirt. This liquor is then clarified as follows: To it is added a minor amount of colloidal bentonite with thorough agitation. The resulting mixture is then allowed to settle and the clarified liquor is separated by decantation or the like from the bottom layer of sludge. In the sludge is most of the dirt and grease originally contained in the wash liquor whereas the clarified liquor is a clear solution of suint. Because of its high suint content and low grease content this clarified liquor has excellent detergent powers. Accordingly, the wool (from the previous water washing step) is scoured with the clarified liquor at an elevated temperature. The scoured wool is then separated from the residual liquor by wringing or the like. The scoured wool is white and has a low grease content on the order of 1%. The residual liquor can be treated by the same clarification process as previously described. The clarified liquor can, if desired, be recirculated in part to the washing or scouring tank or it may be discarded. In the latter event, the clarification treatment so decreases the grease and biological oxygen demand of the 3 liquor that it can in many cases be' directly discharged into the stream or sewer. The scoured Wool because of its low grease content can be directly used in many applications. If a wool of lower grease content is desired it may be further scoured, for example, with an aqueous solution of a non-ionic detergent. In this regard it is to be noted that the non-ionic detergent need only be used in very low concentration (about 0.05%) whereas in conventional non-ionic detergent scouring a much higher concentration of detergent (about 0.3%) is required because of the high grease content of the wool under treatment.

The process of the invention is further explained in connection with the attached drawing which is a flowsheet diagram of the process.

Raw wool is introduced into the washer l, which may be, for example, the first bowl in a conventional Wool-washing train. Water with no added ingredients and at about room temperature is simultaneously added using a large excess of water to wool, usually about 75 to about 300 grams of wool per liter of water. These proportions are not critical and may be varied depending on the cleanness or dirtiness of the wool in question. While in bowl 1, the wool is gently agitated to get good contact with the water, then removed through conventional squeeze rolls and introduced into bowl 2.

The wash liquor from bowl 1 is pumped into mixer 3 where it is thoroughly agitated with a minor proportion of colloidal bentonite on the order of 0.05 to 0.20% (based on the weight of the wash liquor). It is obvious that greater or lesser amounts of bentonite may be required depending on the grease content of the liquor in question. The optimum concentration of bentonite to use in any particular case can easily be determined by conducting a few pilot experiments employing different concentrations of bentonite and observing the sample which gives rapid and elfective grease separation.

The mixture of wash liquor and bentonite is then pumped into settler 4 where the mixture is allowed to stand to cause a separation of the sludge from the clarified liquor, the sludge being withdrawn via pipe 5 and the clarified liquor via pipe 6. Usually the clarification treatment is conducted at about room temperature. Elevated temperatures may be used Without greatly affecting the process but no particular advantage is gained by doing so.

In bowl 2, the washed wool is contacted with the clarified wash liquor being a clear aqueous solution of suint. In this scouring operation a temperature of about 130 to about 160 F. is employed to obtain good scouring eifect. The scoured wool is then removed through conventional wringer rolls. The waste liquor from bowl "2 may then be subjected to a bentonite clarification treatment in mixer 7 and settler S as set forth above in connection with the treatment of the wash liquor from bowl 1. The sludge and clarified liquor are Withdrawn through pipes 9 and 10, respectively. Part of the clarified liquor may be circulated to bowl 2 for scouring of another batch of water-Washed wool or part of it may be recirculated to bowl 1 to increase the amount of grease removed in the washing step, the remainder of the clarified liquor may be discarded directly because of its low biological oxygen demand and low grease content.

The sludge from pipes 5 and 9 may be processed, as by extraction with a fat solvent, for recovery of wool grease therefrom.

In the clarification treatment of this invention, the only material added to the wash or scouring liquor is the colloidal bentonite. The pH of the liquor, which is generally about 7.5 to 9 because of the presence of the somewhat alkaline suint salts, is not altered. Thus it has been observed that at such alkaline pI-Is the bentonite does not adsorb any substantial part of the suint salts but these remain in solution in the clarified liquor. Were one to acidify the liquor during the clarification treat ment it would be found that the bentonite would adsorb most of the suint so that the clarified liquor would have little if any detergent activity. It is also to be noted that it is surprising indeed that the bentonite treatment at alkaline pI-Is is successful to clarify the liquors. Thus it has been previously shown by this inventor (patent application Serial No. 456,084, filed September 14, 1954) that clarification of waste liquor from the conventional soap and soda scouring process or neutral nonior'iic process is effective with bentonite only under acid conditions. Thus the present process which involves clarification with bentonite at alkaline conditions involve a truly unexpected result. Another advantage of conducting the clarification at an alkaline pH is that no corrosion problems are involved and no expense is involved for addition of acid. In clarification treatments under acid conditions, the cost of the added acid is an appreciable expenseand the corrosion problems require the use of expensive acid-resistant materials for the treatment vessels.

It is to be noted that the bentonite used in the present process is a form of bentonite known as colloidal or dispersible. The particles of the material are so minute that they exhibit colloidal phenomena. For example, they form stable dispersions in water which do not settle even after long standing. The dispersions exhibit Brownian movement and other typical colloid characteristics. It has been observed that grades or types of bentonite which are not made up of colloidal particles cannot be used in the process. as they are relatively ineifective in the clarification treatment. Likewise it has been observed that conventional filter aid materials such as diatomaceous earth, kaolinite, fullers earth, etc. do not yield results comparable with those obtained with colloidal bentonite.

The invention is further demonstrated by the following example. i

(A) Raw wool (grease content 12%) was washed for 2 minutes with ordinary tap water using 150 grams Wool per liter of water. The washed wool was separated from the wash liquor and squeezed between rolls to wring out excess liquor. The washed wool had a grease content of 8%. i

The wash liquor (pH about 8) was divided into a series of 100 cc. aliquots, each of these samples being treated with a different proportion of colloidal, dispersible bentonite (KWK Volclay-American Colloid (10.), the proportions being set forth below. In each case the sample of liquor and bentonite (added as a 5% dispersion in water) was agitated then allowed to stand for one hour at room temperature. The clarified liquor was then drawn oif the sludge and subjected to tests as described below. In one case (sample No. 1), no bentonite was added thus to furnish comparative data. In this case the wash liquor was allowed to stand one-hour at room temperature and the liquor drawn oil? the small amount of sludge and tested in the same manner as the other samples.

The turbidity of the liquors was determined with a spectrophotometer, measuring the amount of light (1000 mu) absorbed by the liquor. The units used are arbitrary and based on a turbidity of zero for distilled water. In these measurements the higher the reading, the more turbid is the liquid.

The grease content of the liquors was determined by reducing the liquor to dryness and acidifying and extracting with chloroform.

The colloidal bentonite used in the experiments had the following particle size distribution:

96 to 97% finer than 44 microns 93 to 94% finer than 5 microns 87 to 89% finer than 0.5 micron to finer than 0.1 micron found to be 4.44.

The results obtained are tabulated below:

Sample No 1 2 3 4 (control) Concentration of bentonite, percent. 0. 05 O. 0. Turbity of liquor 3. 2 2. 4 1. 9 Grease content of liquor, p.p.m 8, 100 3, 700 2, 300 2, 000 Reduction in grease content of liquor, percent 54. 4 71. 6 75. 3 Suint concentration in liquor,

p.p.m 20, 500 20, 300 19, 200 17, 500

1 None added.

(B) The clarified liquor from sample #3 was heated to 60 C. and the washed wool from step A was scoured with this liquor employing a proportion of wool to liquor of about 150 grams wool per liter of liquor. The Wool was agitated in the liquor for about 2 minutes then squeezed to remove excess liquor. The scoured wool was rinsed with water, dried, and found to have a grease content of about 1% and to be white in color.

The waste liquor from this scouring step, which had a pH of 7.8, was-agitated with 0.15% of its weight of colloidal bentonite. The bentonite used in this instance was the same as in part A, above. The mixture of liquor and bentonite was allowed to stand for one hour at room temperature. The clarified liquor was drawn oif from the sludge and its turbidity was measured as described above. The turbidity of the clarified liquor was found to be 1.52.

For comparative purposes a sample of the waste liquor, without addition of any bentonite, was allowed to stand for one hour at room temperature. The liquor was drawn off the sludge and the turbidity of this liquor was Having thus described the invention, what is claimed is:

1. A process for scouring wool which comprises washing raw wool with substantially pure water, separating the wash liquor and the Washed wool, the wash liquor having an alkaline pH due solely to its suint content, adding to the wash liquor solely a minor proportion of colloidal, dispersible bentonite to form a mixture having an alkaline pH, allowing the mixture to stand without altering its pH to form a clarified liquor and a sludge, separating the clarified liquor containing suint salts and water from the sludge containing bentonite, grease, and dirt, and thereafter scouring the washed wool with said clarified liquor.

2. A process for clarifying a wool treatment liquor containing dirt, grease, suint, and water, said liquor having an alkaline pH due solely to its suint content, which comprises adding to the liquor solely a minor proportion of colloidal, dispersible bentonite to form a mixture having an alkaline pH, allowingthe mixture to stand without altering its pH to form a clarified liquor and a sludge, and thereafter separating the clarified liquor containing suint salts and water from the sludge containing bentonite, grease, and dirt to recover the clarified liquor for use as a Wool scouring agent.

References Cited in the file of this patent UNITED STATES PATENTS 2,345,827 Olin Apr. 4, 1944 FOREIGN PATENTS 273,755 Great Britain Oct. 3, 1927 319,026 Great Britain Sept. 16, 1929 508,371 Great Britain June 29, 1939 

1. A PROCESS FOR SCOURING WOOL WHICH COMPRISES WASHING RAW WOOL WITH SUBSTANTIALLY PURE WATER, SEPARATING THE WASH LIQUOR AND THE WASHED WOOL, THE WASH LIQUOR HAVING AN ALKALINE PH DUE SOLELY TO ITS SUINT CONTENT, ADDING TO THE WASH LIQUOR SOLELY A MINOR PROPORTION OF COLLOIDAL, DISPERSIBLE BENTONITE TO FROM A MIXTURE HAVING AN ALKALINE PH, ALLOWING THE MIXTURE TO STAND WITHOUT ALTERING ITS PH TO FORM A CLARIFIED LIQUOR AND A SLUDGE, SEPARATING THE CLARIFIED LIQUOR CONTAINING SUINT SALTS AND WATER FROM THE SLUDGE CONTAINING BENTONITE, GREASE, AND DIRT, AND THEREAFTER SCOURING THE WASHED WOOL WITH SAID CLARIFIED LIQUOR. 